The research and development of comprehensive evaluation and management system for harmonic and negative-sequence

Power quality interference sources generate a large number of harmonics and negative-sequence current into power grid in the process of using electricity. Harmonics and negative-sequence current not only affect power grid´s safety and economical operation also cause interference to other normal users, which brings large threat and danger to the power grid and users. As an effective method to prevent and control power quality interference source, it is important to evaluate the harmonic and negative-sequence current at the installation part of power quality interference source, guide the user taking measures to control power quality in the design of current electricity-consummation. This paper describes the research and development of comprehensive evaluation and management system for harmonic and negative-sequence current. This software has the following functions: harmonic computation, comprehensive assessment of user harmonic and negative-sequence, filter design and checking, SVC measurement, harmonic source database management. This software models the system components, load and typical harmonic source under the CIGRE standard with graphical interface. It models the power supply network by the means of one-line diagram, completes the harmonic calculation by Monte-Carlo or Laguerre polynomial, and simulates the distribution of power system harmonics by statistical moment with harmonics power flow techniques. The evaluation of user´s harmonic and negative-sequence based mainly on the GB, combined with the access point short-circuit capacity, power capacity and protocol capacity to calculate the limit value of harmonic and negative-sequence current that assigned to user. According to the typical user´s harmonic emission level or measured value, we can calculate the value of harmonic current generated by user and execute assessment by comparing them. One way to design filter and carry on SVC evaluation is calculating by custom method. Another way is to cut the ex- - isting data into calculation and checking, and then the bus voltage waveform before and after inputting filter or SVC by graphical virtual operation can be obtained, and a rich and intuitive results reports and graphics can be generated at the same time. This software is easy to operate, and its calculation results are accurate. It is an effective tool to assess and manage power quality.